A problem common to zinc-alkaline batteries is the corrosion of the anode zinc caused by the electrolyte. Namely, zinc is so reactive in an alkali electrolyte as reacting with the electrolyte during long term storage, thereby undergoing self-corrosion in accordance with the following equation: EQU Zn+4OH.sup.- .fwdarw.Zn(OH).sub.4.sup.2- +2e.sup.- EQU 2H.sub.2 O+2e.sup.- .fwdarw.2OH.sup.- +H.sub.2 .uparw.
Hydrogen gas generated from the corrosion causes a gas pressure in the battery to elevate, which has the danger of causing leakage of electrolyte, bursting and the like. Accordingly, it has been hithertofore adopted as an industrial technique to use amalgamated zinc powder which is made by adding about 5 to 10% by weight of mercury to zinc, to increase the hydrogen overvoltage and to suppress corrosion to a practically allowable level. In recent years, however, there has been an increasing social demand to decrease the amount of mercury contained in a battery in order to lower environmental pollution, and various studies have been conducted. For example, methods have been proposed, which use zinc alloy powder formed by adding Pb, gallium, In etc. having a high hydrogen over-voltage into zinc to improve the corrosion resistance and to decrease the mercury concentration rate. Although these methods are effective in corrosion inhibition, they have an adverse effect in that their heavy load discharge performance is deteriorated due to the decrease of mercury concentration rate. Though the reasons why the deterioration of heavy road discharge performance occurs at the decreased mercury concentration rate in these proposed methods are not clear, they are presumably because the anode surface becomes covered with the discharge product of the zinc alloy anode, so that the smooth supply of hydroxide ions onto the zinc surface necessary for a discharge reaction is prevented. Thus, there is a need for a zinc anode of low mercury concentration rate which is excellent in both corrosion resistance and heavy load discharge performance.
Further, it has been proposed, mainly with the view of improving manganese dry batteries, that a good corrosion inhibitory effect can be obtained by using for an anode a zinc alloy formed by adding In to zinc or zinc alloy [Japanese Patent Application Kokoku (Post-Exam. Publn.) No. 3204/58]. Though the description of the above proposal includes the cases wherein besides In, one or more elements selected from Pb, Cd, Al, Mg, iron, chromium, calcium, mercury, bismuth, antimony, silver, silicon, nickel, manganese etc. are added to zinc as an impurity or as an additive, it does not state clearly whether the above-mentioned various elements are each contained as an impurity or added as an effective additive except for the effectiveness of In and Pb used in combination as an additive element. Further, it neither states which element is effective for corrosion inhibition, nor shows the suitable amount to be added except those for In and Pb. Thus, no investigation has ever been made on the effect of combined use of these elements, particularly for a zinc-alkali battery, to find an effective zinc alloy composition.